Human leukocyte antigens (HLAs) can bind and display antigens on the surface of human cells to effector T cells. The two major classes of HLAs, class I and class II HLAs, present both foreign and native antigens. Class I HLAs can bind and present peptide antigens produced intracellularly, including viral and tumor specific proteins, to CD8+ effector T cells (e.g., cytotoxic T cells (CTLs)). In response to foreign antigens presented by class I HLA bearing cells, CD8+ effector T cells can destroy the cells presenting the foreign antigen. Class II HLAs can bind and present peptide antigens that originate extracellularly to CD4+ T cells (e.g., helper T cells). In response to foreign antigens presented by class II HLA bearing cells, CD4+ effector T cells can mount humoral immune responses. HLAs are thought to play a role in certain cancers and autoimmune disorders as well as graft rejection.
Antibodies to HLAs are usually produced by alloimmunization resulting from transfusions, pregnancies or transplants. They have also been found in nonalloimmunized individuals. Morales-Buenrostro et al., Transplantation 86: 1111-15 (2008). Antibodies to HLAs found in transplant recipients have been shown to be a cause of acute and chronic graft rejection. Thus, determining whether a recipient carries antibodies to HLAs of a donor can be important in determining the risk of graft rejection in a recipient.
To date, substrates linked to HLAs have been helpful in the detection of antibodies to HLAs. Samples from recipients are contacted with a substrate, and antibodies that bind to the substrate subsequently can be detected using conventional techniques. Conventional substrates, however, are typically linked to both native and denatured HLAs. Thus, these substrates are limited in their ability to distinguish between antibodies to native and denatured HLAs.
In some instances, antibodies to native HLAs, but not to denatured HLAs, are predictive of graft failure. Cai et al., Transplantation 88(2): 226-31(2009). Therefore, there is a need for compositions and methods capable of detecting antibodies to native HLA without the interference of antibodies to denatured HLAs. Such compositions and methods can be used to prevent prospective donors from being excluded due to false positive signals, for example, when assays screening recipients for antibodies to donor HLAs detect, instead, antibodies to denatured HLAs.